there's a bug reported under kio https://bugs.kde.org/show_bug.cgi?id=264020 but is it really a Dolphin bug?

The fault definitely isn't in Dolphin or Konqueror - they are abstracted away from the actual PTP protocol by KIO itself.

However, the KIO slave could be at fault, due to the methods it attempts to use to discover or interact with PTP devices, which are blocked under the usually restricted permissions. I know it has worked perfectly for me in the past though, and the code has not changed much at all throughout the KDE 4.x series.